The test paper allows the easy and reliable detection of hydrogen sulphide. This gas occurs in the processing of raw oil. It is toxic even in low concentrations. Therefore, critical points are carefully checked.

• Colour change: White to brown-black

Sulphide ions in solution also give a positive reaction. The frequently used lead acetate paper is toxic and needs to be declared as hazardous. Sulphide test paper provides an alternative which is non toxic and safe.

Limit of sensitivity: 1 drop a solution containing 5mg/L sulphide (S²⁻) shows a positive reaction.